1. Field of the Invention
This invention relates to photosensitive electrical devices.
2. Discussion of the Related Art
Many complex systems use electrical control circuits to operate other devices. Some such electrical control circuits use photosensitive materials to control the currents or voltages therein. The photosensitive materials include semiconductors such as gallium arsenide (GaAs).
In a semiconductor, light of an appropriate wavelength optically excites mobile carriers. The optical generation of mobile carriers reduces the resistance of a channel made of the semiconductor. The optically induced change in channel resistance has been used as a trigger for such electrical control circuits.
When a conventional semiconductor is not illuminated, the material still has a significant conductivity. Thus, a channel made from a conventional semiconductor typically supports a significant leakage current when not illuminated. Due to the high leakage current, a conventional semiconductor channel does not function like optically controlled switch.
Various embodiments according to principles of the invention provide a photosensitive switch. The photosensitive switch has a conducting state in which the switch supports a substantial current and an insulating state in which the switch supports, at most, a low leakage current. The photosensitive switch goes rapidly from the insulating state to conducting state when illuminated by light of an appropriate wavelength. The photosensitive switch is advantageous as a regulator for a high voltage source, because the switch passes, at most, a low leakage current when not illuminated.
One optically controlled switch according to principles of the invention includes first and second electrodes, a channel extending between the electrodes, and a light source. The channel includes a photosensitive organic material. The light source is capable of illuminating the entire length of the channel and of changing the channel from an insulating state to a conducting state.